1. Field of the Invention
This invention provides an easy to open container/closure assembly, more particularly, an easy to open closure/container assembly having a tamper-indicating feature.
2. Discussion of the Art
Two main types of bottle/closure systems that utilize breakaway bands for indicating tampering are currently commercially available. Both types have certain drawbacks. The first type locks the tamper-indicating band in place. This locking mechanism requires simultaneous application of two of forces: (1) the force to overcome thread and sealing surface friction to remove the cap and (2) the force to break the tamper resistance band, thereby resulting in high removal torques and high standard deviations of removal torque. The lowest removal torque that can be achieved with this system is approximately 18 inch pounds on average. This force is too high for elderly users and users suffering from arthritis. The second type involves the separation of the opening force from the force required to remove the tamper-indicating band, by allowing approximately 180° of free rotation of the cap before breakage of the tamper band is initiated. Accordingly, the closure is subject to substantial “back-off” (i.e. loosening) and possible leakage during distribution. This type of closure also does not provide any audible feedback in the area between cap opening and band breakage to reassure the consumer of safety. In both of these types of tamper resistance mechanisms, the force that breaks away the tamper resistant band is angular or circumferential and is applied by the torque of removing the closure.
U.S. Pat. No. 4,991,731 describes problems encountered when packaging consumable products in sealed containers. These problems are described below.
Due to concerns about material cost, container weight, and breakage, suppliers of consumable products desire to manufacture the container from a plastic substance, such as polypropylene, which is relatively inexpensive and may be colored or translucent. A problem arises when attempting to provide a cap for a plastic container, wherein the cap maintains a hermetic seal. Because it is difficult to maintain a hermetic seal in a plastic container, and conventional metal caps and plastic containers expand by a dissimilar amount, metal caps, by themselves, do not maintain a hermetic seals consistently on plastic containers when subjected to retort conditions.
During thermal treatment such as retort conditions, heat causes polymer relaxation or shrinkage, especially in the upper neck portion of the container. Injection or extrusion molded plastic bottles are formed by melting and pressure forming, which create stress and memory in the molecules of the polymer. The introduction of heat during the retort process causes those molecules to relax, so as to actually shrink the diameter of the neck portion of the container. This shrinkage causes severe problems in maintaining a conventional metal cap on a plastic bottle. This shrinkage may also prevent the use of a conventional plastic cap with a plastic bottle.
The problems mentioned above can be overcome by applying a substantial amount of torque when initially capping the bottle. However, the amount of torque necessary to maintain a conventional cap on a plastic bottle is so high that a person would not be able to easily twist the cap off the bottle following retort. Other alternatives would be to use an extremely expensive plastic to fabricate the bottle so that the plastic would not shrink at retort temperatures and could maintain an internal vacuum without distortion.
Screw on bottle caps have a tendency to loosen from a tightened condition on a threaded bottle neck finish. This tendency to loosen is often referred to as “back off”. This tendency to loosen has a number of causes, including, for example, temperature change, creep in the bottle and cap materials, relaxation of a liner or sealant material, and vibration during handling and shipping. This problem is more frequently encountered when the screw threads have a high pitch to enable the cap to be quickly removed and reinstalled with limited twisting action. Loose caps create problems for the manufacturer and retailer of packaged goods and even for the ultimate user. Loose caps can falsely indicate tampering, and, of course, allow spillage or leakage of the contents as well as entrance of contaminants into the container. A good moisture seal is especially important, for example, when pharmaceuticals and dietary supplements can be adversely affected by excess increases of or by excess decreases of moisture content. While “anti-back off” features are known in the industry, these features have not generally been available for bottles intended for use by elderly persons having limited strength and by sufferers from arthritis.
U.S. Pat. No. 6,296,130, EP 0 864 504 A1, WO 01/15988 A1, U.S. Patent Application Publication 2003/0160020 A1, and U.S. Pat. No. 4,349,116 disclose closure/container assemblies having “anti-back off” features. It is apparent that there is a need for an improved container/closure assembly that provides system seal integrity during retort, as well as permitting the sanitary opening of the container in a single action motion with a very low removal torque.
U.S. Pat. No. 4,813,561 describes containers and closures having tamper resistance bands. This patent describes ratchet teeth on a closure and sets of corresponding teeth on the container that engage below a retaining ledge. The sets of teeth on the container create gaps or spaces into which the tamper band can deform upon opening. However, due to the exact correspondence and alignment of the ratchet teeth on the container and closure, significant torque is still needed to break the tamper band bridges and remove the closure.